[Ifeffit] Cadmium K-edge

[Alan Du]

Hi Bhoopesh and Scott,

I should have given a description of my project. Yes Scott, the work is to
investigate the binding mechanisms of aqueous cadmium onto sodium titanate
nanotubes. Spectrum of Sample 1 and 2 obtained from merging 9 scans and 4
scans, respectively.

A quick check in Athena and, indeed, the white line of Samples are higher
than CdO. I'm not sure the reason behind it though. It is likely that
cadmium binds to the surface of substrate rather than inside the bulk. The
lack of distinct peaks after 1.8 Å means that there are not many scatters
around the absorber?

Bhoopesh, as requested, I have attached the real part of FT (
http://img585.imageshack.us/i/ftreal.jpg/). I haven't got a chance to
interpret them.

>From preliminary fitting of Sample 1, the major and minor peaks at 1.8 and
2.3 Å could be described by a Cd-O path (CdO). This interests me because
Sample 2 does not have a peak at 2.3 Å, meaning there is another single
scattering path for Sample 2?.

The peaks at 3 Å were fitted with Cd-Ti path (CdTiO3). No multiple
scattering paths used. The best fit goes something like this:

****************************************************************************
Independent points          =      13.166992187
Number of variables         =       8.000000000
Chi-square                  =    1534.709946959
Reduced Chi-square          =     297.021921317
R-factor                    =       0.000128095
Measurement uncertainty (k) =       0.000060423
Measurement uncertainty (R) =       0.004455442
Number of data sets         =       1.000000000

Guess parameters +/- uncertainties  (initial guess):
  amp             =     0.9242390   +/-      0.0509920    (1.0000)
  enot            =     1.3950420   +/-      0.5425380    (0.0000)
  delr            =    -0.0872060   +/-      0.0051060    (0.0000)
  ss              =     0.0113250   +/-      0.0008480    (0.0030)
  amp_2           =     0.2441320   +/-      0.1905250    (1.0000)
  enot_2          =    22.5261260   +/-      4.5990590    (0.0000)
  delr_2          =     0.2510860   +/-      0.0719080    (0.0000)
  ss_2            =     0.0274690   +/-      0.0128040    (0.0030)

Correlations between variables:
       amp_2 and ss_2       -->  0.9342
      enot_2 and delr_2     -->  0.9133
         amp and ss         -->  0.8865
        enot and delr       -->  0.8632
       amp_2 and delr_2     -->  0.3040
      delr_2 and ss_2       -->  0.2888
All other correlations are below 0.25

  k-range             = 2.000 - 9.000
  dk                  = 1.000
  k-window            = hanning
  k-weight            = 3
  R-range             = 1.000 - 4.000
  dR                  = 0.000
  R-window            = hanning
  fitting space       = R
  background function = none
  phase correction    = none


  R-factor for this data set   = 0.00270

***********************************************************************************

The above enot_2 is on the high side. I am not entirely familiar with the
parameters yet. Are there other parameters I should worry about?


Cheers,

Alan J. DU
Nanyang Technological University, Singapore
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